Singer Britney Spears has admitted in a US television interview that her second pregnancy has transformed her into an "emotional wreck".

The pop star, who occasionally wept during NBC's Today show, blamed her hormones on swinging between hysterical laughter and crying.

She called recent photos of her driving with her son on her lap "cheap shots", and asked to be left alone.

"We just need privacy and we need our respect," said Spears.

Spears added in the interview with NBC presenter Matt Lauer that she had sat in her father's lap as a child while he drove.

Motherhood

The singer denied that she is estranged from husband Kevin Federline, saying he was helping her to overcome the emotional turmoil of her pregnancy, now in its seventh month.

"He helps me. He has to. I'm an emotional wreck right now," said Spears. "Not in a bad way. Just, you know, I'll start laughing hysterically and then I'll just start crying. It's my hormones," said the star.

The 24-year-old confirmed on the David Letterman show last month that she was expecting another child with Federline, who she married in 2004.

The couple already have one son, Sean Preston, born in September 2005. Spears' music career has been put on hold while she concentrates on being a mother.